Steering pumps are commonly used in the relevant art, for instance, to facilitate a machine operator's ability to steer, maneuver or otherwise control vehicles, work machines, and the like. As a safety feature, some machines are integrated with emergency steering mechanisms which provide an alternative or a secondary power source designed to supply backup power to the steering pump in emergency situations. Such emergency steering systems enable the operator to maintain control of the machine or vehicle in the event of a failure in a primary pump, such as due to leakage, a pump malfunction, or the like.
Emergency steering mechanisms are also further implemented with an operational readiness test or feature that is automatically performed at machine startup to ensure proper functionality of the emergency system. In a typical operational readiness test, the emergency steering pump is briefly activated to determine if the resulting pressure supplied by a secondary pump is sufficient to take over the steering system if necessary. Correspondingly, the typical emergency steering mechanism requires means to rapidly accumulate pressure within a relatively short period of time.
Conventional systems with electrically driven emergency steering mechanisms rely on steering pumps with a fixed pressure relief valve adapted to provide rapid pressure accumulation that is sufficient for not only the operational readiness tests at startup but also for actual emergency conditions. However, such systems accumulate pressure irrespective to the overall system or demands thereof and force the emergency pump to operate at maximum relief. Due to the high levels of pressure involved and the time required to reach threshold pressures, these assemblies are prone to premature failure such as overheating conditions in the electric motor and/or associated motor relays.
Also used in the art are unloader-type steering pumps which allow the emergency pump to build pressure based on system demand, and thereby reduce premature failures commonly associated with pumps using fixed pressure relief valves. Unloader-type steering pumps provide some advantages, but unlike an emergency pump using a fixed relief valve, an unloader-type emergency steering pump alone may not provide the output pressure needed for differentiation over the primary pump standby pressure required to satisfy the operational readiness test.
The present disclosure is directed at addressing one or more of the deficiencies set forth above. However, it should be appreciated that the solution of any particular problem is not a limitation on the scope of this disclosure or of the attached claims except to the extent expressly noted. Additionally, the inclusion of any problem or solution in this Background section is not an indication that the problem or solution represents known prior art except as otherwise expressly noted.